Multiple Cisco products incorporate a version of the OpenSSL package affected by this vulnerability that could allow an unauthenticated, remote attacker to cause certain checks on untrusted certificates to be bypassed, enabling the attacker to forge "trusted" certificates that could be used to conduct man-in-the-middle attacks.

This advisory will be updated as additional information becomes available.

Cisco will release free software updates that address this vulnerability.

No other Cisco products are currently known to be affected by this vulnerability.

Details

The OpenSSL Project disclosed a vulnerability on July 9, 2015. This vulnerability affects both client and server installations of OpenSSL.

OpenSSL Alternative Chains Certificate Forgery Vulnerability

OpenSSL contains a vulnerability that could allow an unauthenticated, remote attacker to cause certain checks on untrusted certificates to be bypassed, enabling the attacker to forge "trusted" certificates that could be used to conduct man-in-the-middle attacks.

The vulnerability is due to an error in the implementation of the logic for finding an alternative certificate chain if the first attempt to build such a chain fails. An unauthenticated, remote attacker could exploit the vulnerability by submitting a crafted certificate chain to an affected device during SSL, TLS, or DTLS authentication. A successful exploit could allow the attacker to cause certain checks on untrusted certificates to be bypassed, enabling the attacker to forge "trusted" certificates that could be used to conduct man-in-the-middle attacks.

The impact of this vulnerability on Cisco products may vary depending on the affected product.

For Cisco products, please refer to the information provided in the Cisco bug IDs listed in the Affected Products section of this document. Additional information and detailed instructions are available in the Cisco installation, configuration, and maintenance guides for each product. If additional clarification or advice is needed, please contact your support organization.

This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) ID CVE-2015-1793.

Workarounds

For potential workarounds on a specific Cisco product, refer to the Cisco bug ID, which is available from the Cisco Bug Search Tool.

Fixed Software

When considering software upgrades, customers are advised to consult the Cisco Security Advisories, Responses, and Alerts archive at http://www.cisco.com/go/psirt and review subsequent advisories to determine exposure and a complete upgrade solution.

In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.

Exploitation and Public Announcements

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

This vulnerability was publicly disclosed by the OpenSSL Project on July 9, 2015.

Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.

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Cisco Security Vulnerability Policy

To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.